Process-induced defects and optical memory in gallium nitride

Effects of dry processing on the band-edge, blue and yellow luminescence be haviour of GaN surfaces exposed to SF6 and Ar plasmas have been investigate d. Our results indicate that a higher concentration of donor-related defect s are introduced on the GaN surface after Ar compared to SF6 plasma treatme nt. The higher defect concentration can be correlated to the yellow lumines cence. In particular, the sample exposed to Ar plasma exhibits a factor of 20 increase in yellow luminescence intensity compared to the unetched sampl e. This effect is attributed to the introduction of defects - metastable st ates on the GaN surface after ion bombardment. Using a laser beam in the ul tra-violet region, we have been able to write to and read from regions on t he Ar-bombarded GaN surface. We demonstrate that the presence of reactive i on etch-induced metastable defects is central to the observed enhanced opti cal memory effect. The etch-induced defects are identified as nitrogen defi cient surfaces limited to the top few monolayers, as well as unidentified d efect propagation down to at least 100nm from the etched surface.